This proposal seeks to formally create a research network to understand how and why the United States is increasingly falling behind virtually all comparably developed/wealthy nations, and even some developing countries, on major indicators of population health, despite the U.S. spending far more than any nation on health care and insurance. Limitations in data comparability across nations currently make comparative analysis of these issues difficult, and the proposed network and other scientists will be working to alleviate these limitations. However, understanding how and why portions of our population exhibit poor and/or worsening health is crucial to understanding America's paradoxical decline in health despite burgeoning spending for health care and insurance. Thus, the network will focus initial efforts on working across many existing sources of data to understand: 1) how and why the health of American women has been worsening since 1980 relative to both American men and women in other countries; 2) how and why socioeconomic disparities in health, especially by education, have persisted and even increased over the past three decades; and 3) how and why racial-ethnic disparities in health exist and persist, while also alleviating in some ways in recent decades. This work will later lead the network to: 1) systematic projection of past, present and especially future trends in U.S. population health and health disparities and the implications for expenditures on health care and insurance; and 2) comparative research to understand what factors have been most important in the worsening of America's population health relative to other comparably developed/wealthy nations. The network will bring together multidisciplinary teams of investigators from three institutions that have been leaders in research on social and biomedical determinants of population health and health disparities: Univ. of Michigan, Univ of Southern California/UCLA, and the Univ. of Texas at Austin. Key scientists from other institutions will be added to the network and/or will interact and collaborate with it via annual meetings and/or ongoing working groups. We seek to generate and disseminate new scientific analyses and findings, and to facilitate development of methods and data that can improve these analyses.